1. Technical Field
The present invention relates to an ultrasonic sensor.
2. Description of the Related Art
The present invention relates to an ultrasonic sensor for sensing a rear area of a vehicle, and more particularly, to an ultrasonic sensor used in a rear stabilization device for a vehicle sensing an obstacle at the time of backing of the vehicle to thereby prevent an accident beforehand.
An ultrasonic sensor generally generates an ultrasonic wave by converting electric energy into mechanical vibration. This ultrasonic sensor has been used in home products such as an ultrasonic humidifier, an ultrasonic stimulator, an ultrasonic skin massager, industrial fields such as an ultrasonic cleaner, an ultrasonic welding machine, an ultrasonic sensor for precision measurement, or the like, a sound detector in a submarine for military purposes, a fish-finder for fishing purposes, and an ultrasonic diagnostic apparatus, an ultrasonic hydro-therapy apparatus, or the like, for medical purposes.
Particularly, the ultrasonic sensor radiates an ultrasonic wave having a predetermined frequency to a target material such as air, water, or the like, receives a signal returned by reflection, and then analyzes the received signal. Therefore, the ultrasonic sensor is used for distance measurement, terrain exploration, hydrographic survey, or the like and may be usefully used particularly under water in which the use of an electric wave or a light wave is significantly limited.
This ultrasonic sensor is configured to include an ultrasonic transducer configured of a piezoelectric element generating an ultrasonic wave having a predetermined frequency, an acoustic matching layer for increasing transfer efficiency of the ultrasonic wave, and a rear surface matching layer for controlling the entire vibration; and a case receiving the ultrasonic transducer in an inner space thereof, wherein an empty space between an inner surface of the case and the ultrasonic transducer is filled with a predetermined molding material, such that the case and the ultrasonic transducer are integrated with each other, thereby having waterproof and impact resistance characteristics.
Meanwhile, the piezoelectric element may have a disk shape or a ring shape. However, it is advantageous that the piezoelectric element has a ring shape in order to allow a molding material having a predetermined viscosity to be completely filled without a portion at which the molding material is incompletely filled during a molding process of the molding material.
Meanwhile, in the ultrasonic sensor according to the prior art as described above, the inner surface of the case is flat, such that the ultrasonic transducer configured of the piezoelectric element, the acoustic matching layer, and the rear surface matching layer is unstably coupled and fixed to the inner surface of the case in a state in which it is received in the case through the molding material.
Particularly, when there is non-uniformity in a transfer path of an ultrasonic wave from the piezoelectric element to an ultrasonic wave radiation surface through the acoustic matching layer, a molding layer, and the case, characteristics of the ultrasonic sensor may be significantly deteriorated. Therefore, careful attention needs to be paid to a manufacturing process.
The ultrasonic sensor according to the prior art having the above-mentioned characteristics had many problems. For example, a sound absorbing material serving as a sound absorbing material and a piezoelectric substance are embedded in an inner portion of the case and the sound absorbing material is attached to an upper portion of the piezoelectric substance, such that when the piezoelectric substance vibrates, the vibration is blocked by the sound absorbing material, thereby deteriorating characteristics of the ultrasonic sensor.
Therefore, research into a structure for solving the problem of the ultrasonic sensor according to the prior art as described above has been urgently demanded.